Sentience is awareness, including the ability to experience pleasure or pain (or analogous drives and experiences) and make predictions about the future. A sentient being is sapient to at least some degree, and sentience is in turn a prerequisite for sophonce. Terragen animals are sentient, as are analogous non-terragen bionts, neogens, and various m-life and a-life entities. On the other hand plants and single-celled organisms (and their nonbiological or xenobiont equivalents) are considered non-sentient or minimally sentient. Modern toposophology has long had a variety of technical definitions for the kinds and degrees of sentience, together with associated tests. Some of these date as far back as the primitive investigations of the 1st century BT or before; these in turn owe something to philosophical speculations from the dawn of the Agricultural Age.